There are buses from Bangkok to Bang sean, you can go from Eastern bus terminal(Ekkamai) or you can go from Northern Bus termail (Mo chit). They have airconditioned bus service and will take about 2 hours from Bangkok.

The eastern bus terminal (Ekamai) can be reached easlily by the sky train, while the Morchit or northern bus terminal you may have to go by taxi or public buses. So going to the Ekamai station may be more convenient.